CVE-2020-26250: Base class whitelist configuration ignored in OAuthenticator
Impact
What goes wrong?
The deprecated (in jupyterhub 1.2) configuration Authenticator.whitelist, which should be transparently mapped to Authenticator.allowedusers with a warning, is instead ignored by OAuthenticator classes, resulting in the same behavior as if this configuration has not been set. If this is the only mechanism of authorization restriction (i.e. no group or team restrictions in configuration) then all authenticated users will be allowed. Provider-based restrictions, including deprecated values such as GitHubOAuthenticator.orgwhitelist are not affected.
Who is impacted?
All users of OAuthenticator 0.12.0 and 0.12.1 with JupyterHub 1.2 (JupyterHub Helm chart 0.10.0-0.10.5) who use the admin.whitelist.users configuration in the jupyterhub helm chart or the c.Authenticator.whitelist configuration directly. Users of other deprecated configuration, e.g. c.GitHubOAuthenticator.teamwhitelist are not affected.
If you see a log line like this and expect a specific list of allowed usernames:
[I 2020-11-27 16:51:54.528 JupyterHub app:1717] Not using allowedusers. Any authenticated user will be allowed.
you are likely affected.
Patches
- Replacing deprecated c.Authenticator.whitelist = ... with c.Authenticator.allowedusers = ... avoids the issue. - Update oauthenticator to 0.12.2 - Update jupyterhub helm chart to 0.10.6
If any users have been authorized during this time who should not have been, they must be deleted via the API or admin interface, per the documentation.
Workarounds
Replacing c.Authenticator.whitelist = ... with c.Authenticator.allowedusers = ... avoids the issue.
In the jupyterhub helm chart prior to 0.10.6, this can be done via hub.extraConfig:
yaml auth: allowedUsers: - user1 - user2
hub: extraConfig: allowedUsers: | # set new field not exposed in helm chart < 0.10.6 setconfigifnotnone(c.Authenticator, "allowedusers", "auth.allowedUsers")
For more information
If you have any questions or comments about this advisory:
Open a thread on the Jupyter forum Email us at security@ipython.org
Other sources
OAuthenticator is an OAuth login mechanism for JupyterHub. In oauthenticator from version 0.12.0 and before 0.12.2, the deprecated (in jupyterhub 1.2) configuration Authenticator.whitelist, which should be transparently mapped to Authenticator.allowedusers with a warning, is instead ignored by OAuthenticator classes, resulting in the same behavior as if this configuration has not been set. If this is the only mechanism of authorization restriction (i.e. no group or team restrictions in configuration) then all authenticated users will be allowed. Provider-based restrictions, including deprecated values such as GitHubOAuthenticator.orgwhitelist are not affected. All users of OAuthenticator 0.12.0 and 0.12.1 with JupyterHub 1.2 (JupyterHub Helm chart 0.10.0-0.10.5) who use the admin.whitelist.users configuration in the jupyterhub helm chart or the c.Authenticator.whitelist configuration directly. Users of other deprecated configuration, e.g. c.GitHubOAuthenticator.teamwhitelist are not affected. If you see a log line like this and expect a specific list of allowed usernames: "[I 2020-11-27 16:51:54.528 JupyterHub app:1717] Not using allowedusers. Any authenticated user will be allowed." you are likely affected. Updating oauthenticator to 0.12.2 is recommended. A workaround is to replace the deprecated c.Authenticator.whitelist = ... with c.Authenticator.allowedusers = .... If any users have been authorized during this time who should not have been, they must be deleted via the API or admin interface, per the referenced documentation.
Affected Software
Remediation
Event History
Frequently Asked Questions
What is the vulnerability ID for this issue?
The vulnerability ID for this issue is CVE-2020-26250.
What is OAuthenticator?
OAuthenticator is an OAuth login mechanism for JupyterHub.
What is the affected software?
The affected software is Jupyter Oauthenticator versions 0.12.0 to 0.12.2.
What is the severity of CVE-2020-26250?
The severity of CVE-2020-26250 is medium (CVSS score 6.3).
How can I fix this vulnerability?
To fix this vulnerability, upgrade to oauthenticator version 0.12.2 or higher.